Evaluation of corrosion inhibition capability of graphene modified epoxy coatings on reinforcing bars in concrete

• Epoxy coatings on reinforcing bars are modified by graphene-based derivatives, reduced graphene oxide (rGO) and graphene oxide (GO). • Corrosion resistance of modified coatings is evaluated by visual inspection, and electrochemical and ultrasonic guided wave measurements. • rGO/CNT (carbon nanotubes) coating even with rGO being hydrophobic, underperforms vis-à-vis corrosion resistance in comparison to GO/CNT modified epoxy coated reinforcing bars (rebars). • GO/CNT modified epoxy coated rebars provide a superior dense network or impermeable layers due to the presence of functional groups on the basal planes of GO sheets, thereby providing enhanced prevention of corrosion in comparison with pure epoxy coating. Corrosion of reinforced concrete structures is the one of the biggest problems faced by the construction industry, with billions of dollars spent annually on corrosion control strategies. Epoxy Coated Rebars (ECRs) have been reported to mitigate corrosion in Reinforced Concrete (RC) structures, but due to the inherent brittle nature of epoxy, its usage is limited. In this study we have proposed modified epoxy coatings on rebars using reduced graphene oxide (rGO) and graphene oxide (GO) along with carbon nanotubes (CNTs) and silane agents for improved ductility and corrosion inhibition properties. Hybrid mixture of CNTs and rGO/GO enhances the mechanical strength of the coating matrix whereas silane agents improve dispersion and bonding characteristics of nano fillers. Differently coated mild steel rebars with rGO/GO based coatings were subjected to accelerated impressed current corrosion. Performance of the coatings was evaluated by visual inspection, corrosion current, ultrasonic guided wave measurements, mass loss and residual tensile strength. Our results indicate that compared to rGO, GO in small proportion (0.4 wt% of epoxy resin) performs superior in corrosion inhibition. The GO/CNT nano composites could have potential application in the field of modified ECR reinforced concrete structures.